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Nanostructured p‐n Junctions for Kinetic‐to‐Electrical Energy Conversion
Author(s) -
Briscoe Joe,
Stewart Mark,
Vopson Melvin,
Cain Markys,
Weaver Paul M.,
Dunn Steve
Publication year - 2012
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201200205
Subject(s) - materials science , piezoelectricity , pedot:pss , nanorod , voltage , optoelectronics , band gap , energy harvesting , energy conversion efficiency , electric field , substrate (aquarium) , piezoelectric coefficient , kinetic energy , p–n junction , power (physics) , semiconductor , nanotechnology , polymer , electrical engineering , composite material , oceanography , physics , engineering , quantum mechanics , geology
Piezoelectric ZnO nanorods grown on a flexible substrate are combined with the p‐type semiconducting polymer PEDOT:PSS to produce a p‐n junction device that successfully demonstrates kinetic‐to‐electrical energy conversion. Both the voltage and current output of the devices are measured to be in the range of 10 mV and 10 μA cm −2 . Combining these figures for the best device gives a maximum possible power density of 0.4 mW cm −3 . Systematic testing of the devices is performed showing that the voltage output increases linearly with applied stress, and is reduced significantly by illumination with super‐band gap light. This provides strong evidence that the voltage output results from piezoelectric effects in the ZnO. The behavior of the devices is explained by considering the time‐dependent changes in band structure resulting from the straining of a piezoelectric material within a p‐n junction. It is shown that the rate of screening of the depolarisation field determines the power output of a piezoelectric energy harvesting device. This model is consistent with the behavior of a number of previous devices utilising the piezoelectric effect in ZnO.